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Police in Garden Grove are urgently asking for help finding a patient who escaped from an Orange County mental health facility. They say he's a danger to the community and, in the past, has threatened young children. Lolita Lopez reports for the NBC4 News at 11 p.m. on Friday, May 3, 2013. (Published Friday, May 3, 2013)

Updated at 11:57 AM EDT on Saturday, May 4, 2013

A man who has threatened young children and is obsessed by the killings at Sandy Hook Elementary School escaped from a mental health facility in Orange County, California, Friday, and police were warning the public to be on the lookout for him.

Garden Grove Police Chief Kevin Raney said Nguyen walked away at 4:45 p.m. from Royale Health Care Center at Bristol Street and Warner Avenue in Santa Ana, where he had been detained since December 2012.

Authorities became familiar with Nguyen, who has been diagnosed with schizophrenia and repeatedly detained and institutionalized, in August 2011. At that time, he walked into the Westminster Police Department dressed in camouflage and holding an assault rifle, saying he wanted to "die by cop," Raney said.

The weapon was not loaded, the chief said, adding that Nguyen did not have a permit for the firearm.

Nguyen was questioned, and police found he was fixated on a teacher at a Garden Grove elementary school that he had attended, Raney said, declining to name the school.

"We have statements and we have the firm belief that he is committed, unfortunately, to harming children at this specific school," Raney said.

Nguyen had been detained periodically since then, Raney said, until it became apparent in interviews with him in December that he was obsessed by the massacre that left 26 dead at a Newtown, Conn., elementary school on Dec. 14, 2012.

Nguyen has spoken repeated both about protecting children and endangering them, Raney said.

"He has written manifestos and other writings that are extremely extensive, extremely descriptive," Raney said. "The thoughts that he is having are real to him and there is, unfortunately, a very strong potential that he will act upon those thoughts."

Ten days ago, Nguyen's mother, who lives in Huntington Beach, tried to gain custody of her son at a court hearing, but the judge refused to have him release, Raney said.

Nguyen is described at 5-foot-8-inches tall, 150 pounds and with black hair and brown eyes. Nguyen is of Vietnamese descent.

He was last seen wearing a black hooded sweatshirt, a white T-shirt, gray pants and white shoes.

Authorities across Orange County and some state law enforcement were actively searching for Nguyen